Ab initio potential energy surface calculations have been carried out for the ground and several excited states of the $NO_{2}$ molecule and $H_{2}O^{+}$ ion. These surfaces have been calculated by SCF and limited-CI methods using contracted Gaussian-lobe basis sets of double-zeta quality. Results of these calculations will be presented and discussed for potential surfaces which intersect at $C_{2v}$ molecular conformations, but interact and undergo avoided crossings when the molecule is distorted to $C_{s}$ conformations. An example of such a pair of surfaces is the $1^{2} A^{\prime} - 2^{2} A^{\prime}$ set of $NO_{2}$ electronic states that at $C_{2v}$ conformations are designated $l^{2}A_{1}$ and $l^{2}B_{2}$.